Garlic (Allium sativum L.) is a popular plant in home
gardens and farms where it is typically grown on a small scale for personal use,
local fresh markets, and/or planting stock. In December 2011, a sample of garlic
from a home garden in Missoula Co., MT, was received at the MSU Schutter
Diagnostic Lab. Outer scales were dark, decayed, and sloughing off the bulbs
(Fig. 1). Spores were visible when viewed at 100× magnification under a
dissecting microscope (Fig. 2). Wet mounts of the scale tissue revealed
relatively large, dark conidia with two to five transverse septa and rounded
apical cells. Conidia were borne singly on geniculate conidiophores. Similar
samples were received in 2012 from Sanders and Lake Counties in northwestern
Montana. Based on morphological characteristics, the fungus was identified as
Embellisia allii (Campan.) E.G. Simmons 1971 (synonymous with
Helminthosporium allii Campan. 1924) (2).

Fig. 2. Spores of E. allii on garlic scale as viewed with a dissecting microscope (100x). Photo by L. Skoglund.

The pathogen was isolated from infected garlic samples received by
the Schutter Diagnostic lab and grown on the artificial medium, potato dextrose
agar (PDA). After 6 days under ambient light conditions at a temperature of
approximately 20°C, colonies were dense, grey to olive-brown to black, with
diameters averaging 40 mm. Conidiophores were geniculate and hyaline to brown
with conidia borne singly (Fig. 3). Conidia measured between 23-45 × 10-14 μm;
were generally smooth, obovoid or cylindrical, with round apical cells and a
distal end that is occasionally elongated (Fig. 3). Conidia had 2-7 (average
4-5) thick, transverse septa and occasionally 1-2 oblique septa (Fig. 3).
Chlamydospores were not observed on PDA-grown colonies, although they are known
to develop as colonies mature (3).

E. allii has been reported on garlic worldwide (1). It was most
recently reported in California in 2012 (3). E. allii is not restricted
to garlic and has been shown to also infect leek and onion (3,4). This is the
first report of Embellisia allii causing bulb canker in garlic in
Montana.